1. Field of the Invention
This invention relates to compositions useful as lubricants for spotting fluids in well drilling operations with either oil-based or water-based muds. The compositions of the invention are non-toxic and biodegradable, are especially useful in fast hole drilling, and also function as performance extenders for corrosion inhibitors in high velocity gas, oil or water drilling, production or gathering applications. The invention also relates to a method for making the subject lubricant using a controlled mixing process and distillation under controlled conditions to remove more volatile components and promote esterification and further reaction with amine substituents.
2. Description of Related Art
International Publication Number WO 97/12947, which claims priority based on U.S. Ser. No. 08/538,262, filed Oct. 3, 1995, discloses high flash point, low vapor pressure, cleaning compositions for oil and gas wells, said compositions containing about 40 to 99 weight percent of a fatty acid alkyl ester blend and about 1 to 25 weight percent of at least one lower alkyl glycol ether. The disclosed compositions, when injected into wells, are said to produce a coating on well casings, lines, pumps, pipes and other equipment, to prevent the adhesion and accumulation of paraffins, other related soils, and scale on these parts to help retard corrosion, and to allow more efficient operation and consistent production between cleanings. Preferred fatty acid alkyl ester blends for use in the invention are selected from the group consisting of C1 to C8 esters of C4 to C22 fatty acids. Preferred lower alkyl glycol ethers are selected from the group consisting of ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl either, and mixtures thereof. The optional use of from 1 to 40 weight percent polyoxyalkylene glycol ethers is also disclosed.
Various other prior art drilling fluid additives, spotting fluids and lubricant compositions are disclosed, for example, in U.S. Pat. Nos. 2,500,163; 3,108,068; 3,298,954; 3,396,105; 4,263,465; 4,282,392; 4,436,636; 4,464,269; 4,502,963; 4,525,285; 4,587,368; 4,652,385; 4,876,017; 5,421,907; and 5,547,925.
A well lubricant composition is needed that has a low acid number, and is therefore much less likely to form calcium soaps from lime in downhole formations, which can in turn cause undesirable foaming in drilling muds. The desired composition should also be nontoxic and not susceptible to foaming during manufacture.
The composition of the invention is a well lubricant, solvent and emulsifier that is preferably formed by the sequential reaction and subsequent distillation of a tall oil fatty acid having a moderately low rosin content with a fatty alkanolamide, preferably in the presence of methyl ester of fatty acids, and most preferably when further reacted with an emulsifier such as coconut oil diethanolamide or an amide of aminoethylpiperazine (AEP) under distillation conditions facilitating the removal of water and lighter reaction byproducts . The fatty acids and oils useful in the invention can range from C8 to C24, with C12, C14, C16, C18 and C20 fatty acids and oils being most preferred. The use of methyl ester is preferred because it functions as a foam supressant, diluent and amine scavenger during distillation.
The composition of the invention has low viscosity compared to tall oil amides and imidazolines, predominantly remains in the oil phase, and is easily dilutable in pale oils, white oils, polyalpha or internal olefins, methyl esters or terpenes, d-limonenes, dipentenes, and the like. In aqueous solution the invention forms a dispersion that, when static or quiescent, evolves completely to oil, not leaving a residual material to sheen or cloud the water. The composition of the invention provides strong adhesion and oil wetting to metal parts, thereby reducing wear, increasing lubricity and improving fast hole drilling.
The compositions of the invention, in their most preferred form, are believed to have the following general molecular structure: 
wherein R1 is distilled tall oil or coconut oil; R2 is low rosin tall oil, vegetable oil or distilled tall oil; and R3 is vegetable oil, tall oil or distilled tall oil.
A method is disclosed herein for producing the lubricant composition of the invention by combining and reacting the components within a controlled temperature range over a prolonged period and distilling off water and volatile reaction byproducts. The reaction and distillation can be done under pressures such as 45 to 120 psig using an autoclave or other pressure vessel in combination with a conventional overhead condenser system, or can be done at approximately atmospheric pressure (slight vacuum to 5 psig) using a conventional stirred reactor vessel that is vented to a condenser or to another chilled vessel that functions as a condenser.
According to a preferred method of the invention, the preferred components are combined and mixed inside a stirred reactor vessel in fluid communication with a chilled condenser section. The temperature of the reactants is gradually raised to a temperature above 300xc2x0 F., most preferably between about 320xc2x0 and about 350xc2x0 F., using heating means such as steam coils, and maintained at that temperature, usually for about 6 to 8 hours or more, sometimes up to about 12 hours, until the reaction is substantially complete. Distillation is desirably continued until the pressure of reaction reaches zero to facilitate the removal of distillable liquids, sweet perfume and clear liquids, followed by dark distillates of rearrangement.
The reaction product is periodically sampled and the acid number is determined. Sampling is desirably continued on an hourly basis until the acid number is less than about 35, and most preferably, about 25 or lower. Samples are also desirably checked for AEW, which is preferably greater than 1000, and most preferably, ranges between about 2000 and about 5000 as the acid number drops to about 25.
The preferred amides for use in the invention are most preferably made using diethanolamine (DEA), monoethanolamine (MEA), and other hydroxyethylamines that can undergo low temperature esterification and then interchange during the distillation. The oils can react by inter- or trans-esterification. During the process of the invention, the oils, fatty acids or methyl esters are believed to further react with free amine, the amine portion of fatty ester components, and also, the glycerin produced by decomposition of the oils (triglycerides). The subject process is believed to facilitate molecular rearrangement, lower the acid number, increase the amine equivalent weight (AEW), and remove substantially all soaps, water, methanol and low molecular acids and unreacted esters from the product, together with any other species that will steam distill. Removal of the steam-distillable materials eliminates their subsequent vaporization during use, for example, in hot drilling systems.
The products of the invention utilize fatty acids, preferably fatty acids contained in tall oil derived from pine trees, containing about two weight percent rosin, and most preferably, distilled tall oil containing from about 10 to 50% rosin acids. Secondly, the products depend on other vegetable oils or extracts, especially those obtained from coconut or coffee, but can also be made using oils or extracts from soya, safflower, canola, rapeseed, flax, cotton and the like. Distilled tall oil, low rosin tall oil and reclaimed cooking oil can also be used as the xe2x80x9cvegetable oilxe2x80x9d component in making the compositions of the invention. Tall oil fatty acids having from 8 to 24 carbon atoms are preferred, with tall oil fatty acids having C12, C14, C16, C18and C20 fatty acids being most preferred.
The mixing and prolonged heating of the reactants within a controlled temperature range and under distillation conditions, as described in greater detail below, is desired to allow molecules to develop as predicted. Although products formed simply by mixing the reactants may exhibit some of the utility of the product of the invention, rearrangement of the reaction products through inter- and trans-esterification during prolonged heating is believed to be necessary for achieving the full utility of the preferred product of the invention.
The compositions of the invention, in their most preferred form, are believed to have the following general molecular structure: 
wherein R1 is distilled tall oil or coconut oil; R2 is low rosin tall oil, vegetable oil or distilled tall oil; and R3 is vegetable oil, tall oil or distilled tall oil. These compositions are preferably made by combining under controlled reaction conditions as set forth herein components selected from each of the following four principal groups: methyl esters; tall oil fatty acids; esters produced from amides (amide/esters); and amides.
Methyl esters suitable for use in the compositions of the invention include, for example, methyl esters of C16-18 saturated and C18 unsaturated fatty acids, and methyl esters of tall oil fatty acids.
Fatty acids suitable for use in the compositions of the invention include, for example, disproportionated tall oil fatty acids; distilled tall oil; disproportionated tall oil; resin acids and rosin acids; and rosin tall oil.
Amide/esters that are suitable for use in the compositions of the invention include, for example, the reaction product of distilled tall oil and an alkanolamine, particularly diethanolamine or monoethanolamine; N, N-bis (hydroxyethyl) tall oil fatty amides; reaction products of rosin with diethanolamine; and reaction products of tall oil fatty acids with diethanolamine.
Amides suitable for use as emulsifiers in the compositions of the invention include the reaction product of vegetable oil and an alkanolamine, the reaction product of vegetable oil with a polyethylene amine, the reaction product of distilled tall oil with AEP, and the reaction product of distilled tall oil with a polyethylene amine, for example, N,N-bis (hydroxyethyl) saturated and unsaturated C8-18 and C18 amides; reaction products of coconut oil with diethanolamine; and reaction products of these substituents with AEP and other polyethylene amine homologues.
A well lubricant composition of the invention comprises from about 45 to about 90 weight percent of the reaction product of tall oil fatty acid and a fatty alkanolamide, reacted in the presence of up to about 25 weight percent, and more preferably from about 5 to about 25 weight percent, methyl ester of fatty acids, then further reacted and distilled in the presence of from about 5 to about 30 weight percent of the reaction product of a fatty oil with an alkanolamine. The combined weight of the fatty acid and amide/ester components preferably ranges from about 55 to about 90 weight percent of the total reactants, and their ratio of fatty acid to amide/ester desirably ranges from about 2:1 to about 3:2. Where the fatty alkanolamide is the reaction product of distilled tall oil and diethanolamine, the distilled tall oil and diethanolamine are preferably reacted in a ratio of about 3:1 by weight. According to a particularly preferred embodiment of the invention, from about 5 to about 25 weight percent of methyl ester of fatty acids is also added to the initial reactants to scavenge for free amines, suppress foaming, and function as a diluent. The amide component is believed to function as an emulsifier, and is desirably present in an amount ranging from about 5 to about 30 weight percent of the reactants.
A well lubricant composition is disclosed that comprises from about 60 to about 90 weight percent of a first reaction product of distilled tall oil and fatty alkanomide, which is further reacted and distilled in the presence of from about 10 to about 20 weight percent of a second reaction product of distilled tall oil and AEP. The reaction product of distilled tall oil and fatty alkanomide is preferably produced in the presence of from about 5 to about 25 weight percent methyl ester of fatty acids having from about 16 to 18 carbon atoms. One embodiment of the subject well lubricant composition comprises from about 30 to about 60 weight percent distilled tall oil. One embodiment of the subject well lubricant composition comprises from about 30 to about 60 weight percent fatty alkanolamide. In one embodiment of the subject well lubricant composition, the distilled tall oil contains about 25 weight percent rosin. In one embodiment of the subject well lubricant composition, the methyl ester contains about 25 weight percent rosin.
The temperature is preferably further increased until the temperature is above 300xc2x0 F., and most preferably between about 320xc2x0 F. and about 350xc2x0 F., then controlled within that range with continuous distillation until the reaction substantially reaches completion. Completion of the reaction may take from about six to about eight hours, and sometimes up to about 12 hours, from the time that the reactants reach a temperature of at least about 300xc2x0 F.
It is believed that during the reaction, some of the tall oil fatty acid is converted to methyl ester. It is also believed that the presence of methyl ester in the system reacts with unreacted secondary amines that may be present in the amide components, particularly where the amide is a reaction product of distilled tall oil with AEP.
During distillation, the reaction mixture is vented to a condenser vessel or section, whereby distillable liquids, sweet perfume and clear liquids are removed, followed by dark distillates of rearrangement. Distillation is continued until the pressure of reaction reaches zero. The reaction product is sampled and the acid number is determined. Sampling is desirably continued on an hourly basis until the acid number is less than 35, and most preferably, about 25 or lower. Samples are also desirably checked for AEW, which is preferably greater than 1000, and most preferably, ranges between about 2000 and about 5000 as the acid number drops to about 25. It is observed that a weight loss of from about two to about four percent (when comparing weight of the reaction products remaining in the reactor to the weight of reactants at about 180xc2x0 F.) is typical of the compositions of the invention when made as disclosed herein, and such weight loss is believed to be further evidence of substantial completion of the reaction and the associated distillation desired to produce the products of the invention.
The products of the invention will desirably have a pH ranging between 6 and 8, with a range of from about 6 to about 7.5 preferred. A pH in excess of about 8.3 may indicate the presence of free amine, which can be toxic.
The method and composition of the invention are further described and explained in relation to the following examples: